The present invention is directed generally to optical devices, and more particularly to optical devices requiring high precision in the length of an optical element.
Some optical elements require that the length of the optical path through the element be very precise. For example, the thickness of a retardation wave plate should be precise in order to impose the desired degree of retardation at the wavelength of interest. Manufacturing a retardation plate to a precise thickness is commonplace for zero or low order waveplates, since they are relatively thin. However, manufacturing a high order retardation plate, having a thickness of several mm, to a high tolerance in length is more difficult, which leads to increased costs. Furthermore, once an element is fabricated, the optical path length through the element is typically fixed, and is not adjustable. Therefore, if the element is made to the wrong length, the element has to be scrapped and a new one fabricated.
Therefore, there is a need for a method of inexpensively producing optical elements that a precise optical path length and reduces the need to scrap elements of the wrong optical path length.
Generally, the present invention relates to a device and method where the optical path length through an optical element is adjustable with high precision. One particular embodiment of the invention is directed to an optical element having a first segment formed from a first optical material, and having a first face at a first end and a second face at a second end opposing the first face, the first and second faces being disposed on a beam path, the second face being disposed at an angle relative to the first face so as to be non-parallel with the first face. The element also includes a second segment formed from a second optical material, and has a third face at a third end and a fourth face at a fourth end opposing the third face, the third and fourth faces being disposed on the beam path, the third face being disposed at an angle relative to the fourth face so as to be non-parallel with the fourth face. At least one of the first and second segments is translatable across the beam path so as to change an optical path length through the optical element.
Another embodiment of the invention is directed to a method for setting an optical path through an optical element. The method includes providing the optical element as at least two segments having an optical beam passing therethrough, each of the at least two segments having at least one face non-perpendicular to the optical beam. The method also includes translating at least one of the at least two segments across the optical beam so as to adjust the optical path length of the optical beam through the element.
Another embodiment of the invention is directed to an optical element having an adjustable optical path length. The invention includes at least two optical transmission segment means for passing a light beam, the light beam passing non-perpendicularly through at least one face of each of the at least two optical transmission segment means. The invention also includes means for translating at least one of the at least two optical transmission segment mean across the optical beam so as to adjust an optical path length of the optical beam passing through the optical element.
The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and the detailed description which follow more particularly exemplify these embodiments.